Color copying and sheet material therefor

ABSTRACT

A stabilized photosensitive heat-developable sheet material or assembly of sheet materials for making color prints or transparencies by a method involving exposure, heat development, and thermographic transfer.

United States Patent 1 Wiese, Jr. et al.

[ Oct. 23, 1973 COLOR COPYING AND SHEET MATERIAL THEREFOR [75]Inventors: Joseph A. Wiese, Jr.; George Van Dyke Tiers, both of St.Paul, Minn.

[73] Assignee: Minnesota Mining and Manufacturing Company, St. Paul,Minn.

[22] Filed: Feb. 2, 1971 [21] Appl. No.2 111,981

[56] References Cited UNITED STATES PATENTS 2,396,726 Trimble 96/113,280,735 10/1966 Clark 250/65 T 3,301,697 1/1967 Russell 250/65 T3,370,170 2/1968 Gold 350/65 T 3,392,020 7/1968 Yutzy.... 250/65 T3,418,468 12/1968 Marx..... 250/65 T 3,457,075 7/1969 Morgan. 96/1 14.13,502,871 3/1970 Marx 117/36.8

3,520,691 7/1970 Scheler 117/36.8 3,531,286 9/1970 Renfrew 117/36.8

Primary ExaminerNorman G. Torchin Assistant Examiner-Richard L.Schilling AttorneyAlexander, Sell, Steldt & Delahunt [57] ABSTRACT Astabilized photosensitive heat-developable sheet material or assembly ofsheet materials for making color prints or transparencies by a methodinvolving exposure, heat development, and thermographic transfer.

7 Claims, 1 Drawing Figure COLOR COPYING AND SHEET MATERIAL THEREFORThis invention relates generally to the recording of light-images onlight-sensitive heat-developable dry silver sheet materials. In oneaspect the invention relates to modified dry silver sheet materials andto a method of using the same in making colored prints of coloredlight-images. In a particular aspect the invention relates to dry silversheet materials in tri-pack form and to their application in makingmulti-color prints by a method involving but a single exposure, e.g.through a color negative.

Dry silver sheet materials have been described, in U.S. Pat. No.3,457,075, as consisting essentially of (a) photosensitive silver halidecatalyst-forming means and (b) heat-sensitive reactant image-formingmeans including an organic silver salt oxidizing agent and a reducingagent for silver ion, the oxidation-reduction reaction of which toproduce a visible change is accelerated by said catalyst.

The thermographically induced transfer of volatilizable dyes has beendescribed, e.g., in.U.S. Pat. No. 3,280,735, in terms of brieflyexposing to intense infrared radiation a printed original, whereby toproduce a corresponding heat pattern for volatilizing the dye from asource sheet onto a receptor sheet. The heat pattern is subject tolateral diffusion. The combination of intense light and high temperaturehas been found in many cases to cause image blurring of imaged drysilver sheet materials under thermographic copying conditions. 1

It has nowbeen found possible to provide a modified dry silver sheet orcoating with which the'rmographically stable imaged sheets may beproduced. It has also been found possible to employ such sheet materialsin a thermographic image transfer process whereby to produce sharplydefined monocolor or multicolor prints of colored light images, all aswill hereinafter be set forth.

The single FIGURE of the drawing represents in cross-section a portionof a pack of modified dry silver sheets prepared in accordance with theprinciples of the invention and useful in making full-color prints.

Sheet comprises a transparent film support 11 having on one surface amodified dry silver coating 12 and on the .other surface a volatilizabledye 13. Similarly, sheet 14 comprises film 15, dry silver coating 16 anddye coat 17, and sheet 18 comprises film 19, dry silver coating-20 anddye coating 21. The threesheets, assembled as shown, comprise a tripack22.

In making a print, the,tripack 22 is first exposed to a light-image fromthe upper surface as seen in the drawing. After exposure .the threesheets are heated briefly to develop in each-a dense image correspondingto a portion of the light-image, and the three are then successivelyplaced in registry against a receptor sheet and the composite is brieflyexposed to intense infrared radiation, e.g., in a thermographic copyingmachine. The heat patterns induced in the image areas cause transfer ofdye to corresponding areas of the receptor sheet, with production of acolored image. Alternatively, the separate dye images are transferred toseparate transparent film receptor sheets which are then placed inregistry to form a full-color transparency.

In a modification of the method just described, and using a dry silvercomposition which under appropriate development conditions has anegative D log E slope, the exposed sheets are developed in a manner toproduce a positive rather than a negative image. The resulting dyeimages obtained by thermographic transfer from the thus imaged filmsthen represent a direct rather than a color reversed record of theinitial colored light pattern.

The dry silver coatings 12, 16 and 20 are respectively sensitized toblue, green and red light, as indicated in the drawing by the letters B,G and R. The dye coatings l3, l7 and 21 analogously contain yellow,magenta and cyan dyes respectively, indicated as Y, M and C. Thetransparent carrier film is marked T in each instance. The dye layersassist inabsorbing light other than that to which the lower layer orlayers of dry silver material have been sensitized, so that a sharpseparation of color is accomplished and a true showing of both white andblack as well as color is accomplished in the final print or printassembly. The lower dye layers also serve as antihalation layers andassist in providing sharply defined images.

As above indicated, both direct and reverse light patterns may bereproduced as direct color prints. Thus the light pattern may beobtained either by direct reflection from a colored subject or coloredoriginal, or by projection through a colored transparency which may beeither a positive or a negative photographic color transparency.

An important feature of the invention resides in the stabilizing of theimaged dry silver layer against further darkening of the background, orlateral spreading of the image areas, under continued heating orexposure to infra-red. It has been found that various halogencontainingorganic oxidizing agents may be incorpo rated in the dry silver coatingswithout altering the initial light-sensitivity thereof, and'that suchcompounds effectively stabilize the imaged sheet.

Compounds in which a positive halogen is attached directly to nitrogenrepresent a particularly effective class of stabilizers. Compounds suchas N- bromosuccinimide and N,N'-dichloro-N,N-

Aibengoylethylerrediamine are representative. This compound also knownas N,N-dichloro-l,Z-ethyleri bisbenzamide, is a presently preferredstabilizer material. The stabilizer may be incorporated in acompositioncontaining all of the required components for preparing thephotosensitive heat-developable dry silver coating. The more activestabilizers are preferably added in a second coating, the photosensitivecomponents being applied in a separate first coating, to avoid anytendency toward desensitization of the photosensitive materials prior toheat development. I

The following specific Example will serve as a further illustration of.the principles of the invention.

EXAMPLE A first composition is prepared by first dispersing 20 parts byweight of silver behenate full soap in a mixture of 37.5 partsmethylethyl ketone and 42.5 parts toluene, pre fe11bl y byprolongedballmillingig 50 gms. of the dispersion is added 40 ml. of methylisobutyl ketone, 10 ml. of a 2% solution of mercuric bromide in methylalcohol, and 22 gms. of a 15% solution of polyvinylbutyral resin inethyl alcohol, all operations beginning with addition of mercuricbromide being conducted under darkroom conditions. To such mixtures arethen added various spectral sensitizer materi- (3:0 S /o= zs N Et IGreen Sensitizer: add 3 ml. of a .05% solution in acetone.

Red Sensitizer: add 6 ml. of a .05% solution in methanol.

I CHiCHi-C Over the above coatings is then supplied a further coatingconsisting of the following:

3% solution of cellulose acetate butyrate in methylethyl ketone75 ml.20% solution of 'polymethylmethacrylate in ethyl acetateml.

phthalazinonel gm.

2,2'-methylenebis-(4-methyl-G-tertiarybutylplie n'oli l gm.

2% solution of phthalic acid in methanoll.5 ml.

N ,N'-dichloro l ,2-ethylene bisbenzamide 2.75 gm.

The second coating is likewise applied at a wet thickness of 3 mils anddried.

The reverse surfaces of the three coated films are then separatelycoated with the appropriate dyes, the coating solutions in each instanceconsisting of 326 mgm. of dye in 10 gms. ofa 16.7% solution ofacrylonitrile:vinylidene copolymer (Saran F-220) in methylethyl ketone.The yellow dye is Sudan Yellow GR Concentrate, Color Index 21240. Themagenta-dye is 4;

tricyanovinyl-N,N-di-n-butylaniline. The cyan dye is DuPont Oil Blue A,Color Index Solvent Blue 36. Other useful volatilizable dyes includeSudan Yellow RRA, Sudan Yellow GGA, Special Red S Conc., and Smoke GreenNo. l.

- The three coated films are combined in a tri-pack in the relationshipshown in the drawing, and the pack is exposed to a reverse colorlight-image by contact printing through a photographic color negative.The three films are separately briefly heated to form on each a densevisisble image at the light-struck areas. The films are then laidagainst transparent polymeric receptor films, in this case consisting ofthin transparent Mylar polyester film lightly coated with a mixture of1.5 grams of nickel acetate tetrahydrate and 10 grams of polyvinylalcohol applied from solution in grams of water, and are briefly exposedto intense infra-red radiation in a'thermographic copying machine toform on each receptor a monocolor partial negative image. The threeimaged receptor films are placed together in registry to provide a fullcolor positive transparency.

Another tripack assembly is first exposed to a direct color light-imageby contact printing through a photographic color positive serving as anoriginal, and the three films are separately subjected to minimum heatrequired to produce maximum useful density at unexposed areas. By suchcontinued heating the initially darkened light-struck areas aretransparentized while the initially transparent non-light-struck areasprogressively darken to a maximum. The three films are then successivelyplaced against a receptor sheet consisting of white paper lightly coatedwith a mixture of four parts by weight of calcium stearate, two parts ofnickel stearate, four parts of calcium carbonate, and ten parts ofpolyvinyl alcohol, applied in 90 parts of water. The composite is ineach case passed through the thermographic copying machine, the imagedfilm in each case being placed in registry with the position of anypreceding imaged film or films. A direct full-color reproduction of thecolored original is obtained.

In the foregoing Example, exposure is typically between 3 and 6 secondsusing as the light source a 650 watt FAB tungsten filament quartz iodinelamp at a distance of 3 feet, and development is achieved by heating attemperatures between about and C. With other formulations and conditionsit may be found necessary to modify these values, but the necessarymodifications are readily determined by simple preliminary sensitometrictest procedures well within the skill of the art.

What is claimed is as follows:

1. A photosensitive sheet material comprising a transparent thin carrierhaving over one surface a photosensitive heat developable dry silverlayer comprising (a) photosensitive silver halide catalyst-formingmeans, (b) heat-sensitive reactant image-forming means including anorganic silver salt oxidizing agent and a reducing agent for silver ion,the oxidation-reduction reaction of which to produce a visible change isaccelerated by said catalyst, and (c) N,N-dichloro-l ,2-

ethylenebisbenzamide or N-bromosuccinimide, and

said carrier having over the other surface a layer comprising, in apolymeric binder, a dye which is volatilizable therefrom at temperaturesobtained under thermographic copying conditions.

2. Sheet material of claim 1 wherein said dry silver layer contains aspectral'sensitizer for sensitizing said sheet to a primary color.

3. A pack of sheet material useful in making fullcolor prints andcomprised of three sheets of photosensitive sheet material eachcomprising a transparent thin carrier having over one surface aheat-stabilized photosensitive heat developable dry silver layercomprising (a) photosensitive silver halide catalyst-forming means and(b) heat-sensitive reactant image-forming means including an organicsilver salt oxidizing agent and a reducing agent for silver ion, theoxidation-reduction re action of which to produce a visible change isaccelerated by said catalyst, and (c) a spectral sensitizer forsensitizing said sheet to a primary color, and said carrier having overthe other surface a layer comprising, in a polymeric binder, a dye whichis volatilizable therefrom at temperatures obtainable underthermographic copying conditions, and wherein the first of said threesheets carries a cyan dye and is sensitized to red, the second carries amagenta dye and is sensitized to green, and the third carries a yellowdye and is sensitized to blue.

4. A pack ofsheets according to cl ai m {wherein tl e dry silver layerseach contain N,N-dichloro-l,2 ethylene-bisbenzamide orN-bromosuccinimide.

5. Method of making a multicolor print comprising:

(l) exposing to a light-image a pack of three sheets of I photosensitivesheet material each comprising a transparent thin carrier having overone surface a heatstabilized photosensitive heat developable dry silverlayer comprising (a) photosensitive silver halide catalyst-forming meansand (b) heat-sensitive reactant image-forming means including an organicsilver salt oxidizing agent and a reducing agent for silver ion, theoxidation-reduction reaction of which to produce a visible change isaccelerated by said catalyst, and (c) a spectral sensitizer forsensitizing said sheet to a primary color, and said carrier having overthe other surface a layer comprising, in a polymeric binder, a dye whichis volatilizable therefrom at temperatures obtainable underthermographic copying conditions, and wherein the first of said threesheets carries a cyan dye and is sensitized to red, the second carries amagenta dye and is sensitized to green, and the third carries a yellowdye and is sensitized to blue, with said light-image being incident onsaid third sheet; (2) separating the three sheets and heating each oneindependently to develop a visible image; and (3) separately brieflyexposing each sheet to intense infra-red radiation while maintaining thedye layer against a common receptor sheet and with each sheet inregistry with the position of the preceding sheet or sheets.

6. Method of claim 5 wherein the receptor sheet includes a surfacecoating comprising a nickel salt of an organic acid in a water-solublebinder. I

7. Method of making a color print comprising: exposing to a light-imagea photosensitive sheet material comprising a transparent thin carrierhaving over one surface a photosensitive heat developable drysilverlayer comprising (a) photosensitive silver halide catalyst-formingmeans, (b) heat-sensitive reactant imageforming means including anorganic silver salt oxidizing agent and a reducing agent for silver ion,the oxidationreduction reaction of which to produce a visible change l cr siby qsa a mtaadl lNfi q o 1,2-ethylenebisbenzamide orN-bromosuccinimide,

and said carrier having over the other surface a layer comprising, in apolymeric binder, a dye which is volatilizable therefrom at temperaturesobtained under thermographic copying conditions; heating the exposedsheet to develop a visible image; and briefly exposing the imagedsurface to intense infrared radiation while maintaining the dye-carryingsurface against a receptor sheet.

UNITED STATES PATENT 0mm: CERTIFICATE OF CORRECTION Patent: No-3,767,394 Dated Oct. 23, 1973 Inventor) Joseph A. Wiese, Jr. and GeorgeVan Dyke Tiers It is certified that error appears in theabove-identified-patent .and that said Letters Patent are herebycorrected as shown below:

Column 3, lines 21-30 The structural formula of the green sensitizershould be:.

Signed and sealed this 9th day of April 1971;.

(SEA-L) v Attest:

. EDWARD II.FLETCHER,JR. C. MARSHALL DANN Commissioner of Patents FORMPC4050 (10-697

2. Sheet material of claim 1 wherein said dry silver layer contains aspectral sensitizer for sensitizing said sheet to a primary color.
 3. Apack of sheet material useful in making full-color prints and comprisedof three sheets of photosensitive sheet material each comprising atransparent thin carrier having over one surface a heat-stabilizedphotosensitive heat developable dry silver layer comprising (a)photosensitive silver halide catalyst-forming means and (b)heat-sensitive reactant image-forming means including an organic silversalt oxidizing agent and a reducing agent for silver ion, theoxidation-reduction reaction of which to produce a visible change isaccelerated by said catalyst, and (c) a spectral sensitizer forsensitizing said sheet to a primary color, and said carrier having overthe other surface a layer comprising, in a polymeric binder, a dye whichis volatilizable therefrom at temperatures obtainable underthermographic copying conditions, and wherein the first of said threesheets carries a cyan dye and is sensitized to red, the second carries amagenta dye and is sensitized to green, and the third carries a yellowdye and is sensitized to blue.
 4. A pack of sheets according to claim 3wherein the dry silver layers each containN,N''-dichloro-1,2-ethylene-bisbenzamide or N-bromosuccinimide. 5.Method of making a multicolor print comprising: (1) exposing to alight-image a pack of three sheets of photosensitive sheet material eachcomprising a transparent thin carrier having over one surface aheat-stabilized photosensitive heat developable dry silver layercomprising (a) photosensitive silver halide catalyst-forming means and(b) heat-sensitive reactant image-forming means including an organicsilver salt oxidizing agent and a reducing agent for silver ion, theoxidation-reduction reaction of which to produce a visible change isaccelerated by said catalyst, and (c) a spectral sensitizer forsensitizing said sheet to a primary color, and said carrier having overthe other surface a layer comprising, in a polymeric binder, a dye whichis volatilizable therefrom at temperatures obtainable underthermographic copying conditions, and wherein the first of said threesheets carries a cyan dye and is sensitized to red, the second carries amagenta dye and is sensitized to green, and the third carries a yellowdye and is sensitized to blue, with said light-image being incident onsaid third sheet; (2) separating the three sheets and heating each oneindependently to develop a visible image; and (3) separately brieflyexposing each sheet to intense infra-red radiation while maintaining thedye layer against a common receptor sheet and with each sheet inregistry with the position of the preceding sheet or sheets.
 6. Methodof claim 5 wherein the receptor sheet includes a surface coatingcomprising a nickel salt of an organic acid in a water-soluble binder.7. Method of making a color print comprising: exposing to a light-imagea photosensitive sheet material comprising a transparent thin carrierhaving over one surface a photosensitive heat developable dRy silverlayer comprising (a) photosensitive silver halide catalyst-formingmeans, (b) heat-sensitive reactant image-forming means including anorganic silver salt oxidizing agent and a reducing agent for silver ion,the oxidation-reduction reaction of which to produce a visible change isaccelerated by said catalyst, and (c)N,N''-dichloro-1,2-ethylenebisbenzamide or N-bromosuccinimide, and saidcarrier having over the other surface a layer comprising, in a polymericbinder, a dye which is volatilizable therefrom at temperatures obtainedunder thermographic copying conditions; heating the exposed sheet todevelop a visible image; and briefly exposing the imaged surface tointense infrared radiation while maintaining the dye-carrying surfaceagainst a receptor sheet.